This application claims priority under 35 U.S.C. 120 to U.S. Pat. Utility Application Ser. No. 09/191,899 filed Nov. 13, 1998, co-pending, now issued on Apr. 16, 2002 as U.S. Pat. No. 6,373,857 B1.
1. Technical Field
The present invention relates generally to Internet Telephony communication systems; and more particularly to a method and apparatus for distributing load among a plurality of Gatekeepers of the Internet Telephony communication system by redirecting communications from one Gatekeeper to another Gatekeeper.
2. Related Art
Internet Protocol (IP) Telephony systems have been rapidly evolving over the past few years. In an IP telephony system, calls are routed through a packet switched Internet Protocol network (IP network). This compares to call routing in a circuit switched system, such as the Public Switched Telephone System (PSTN), in which calls are routed over dedicated circuits. In a circuit switched network, digitized information making up a call is sent in a continuous stream (when active) from a caller to a called party, and vice versa. However, in a packet switched IP Telephony system, each segment of the call is converted into IP packets, routed through the IP network, reconstructed upon exiting the IP network and then delivered to a called party.
With IP packet switching, as opposed to circuit switching, network bandwidth usage for each call may be reduced because a dedicated circuit is not created for each call. However, as is generally known, IP telephony systems networks cannot presently provide the Quality of Service (QoS) that is provided by circuit switched networks. Thus, IP telephony has yet to obtain the popularity of circuit switched networks for voice communications which require a minimal level of QoS. Nonetheless, IP telephony systems yield acceptable results in some situations, particularly those situations in which PSTN tariffs are great, e.g., international calls. An international call placed and serviced by an IP telephony system can oftentimes be made for the cost of a local phone call.
In initiating a call in an IP telephony system, a calling endpoint couples to the IP network via a source Gateway, oftentimes coupling to the source Gateway via the PSTN or another network, e.g., Local Area Network or Wide Area Network. The source Gateway then interfaces with a Gatekeeper to setup the call. The Gatekeeper sets up the call with a called endpoint, usually via a destination Gateway. The call is then routed from the caller, through the source Gateway, via the IP network to the destination Gateway, and from the destination Gateway to the called party. From the destination Gateway to the called party, the call may be routed via the PSTN. The source and destination Gateways convert the call between IP based data packets that are routed across the IP network and the circuit switched counterparts that are received from, and delivered to the endpoints via the PSTN.
Service providers install the infrastructure required to provide the IP telephony service. In providing the service, the service providers generally route signaling for all calls through their Gatekeepers. By routing the call signaling through their Gatekeepers, the service provider monitors usage for billing purposes, alters IP network routes to compensate for outages and routes calls to various destination Gateways to balance load upon the destination Gateways.
In a typical IP telephony system, the service provider initially installs and maintains a single Gatekeeper that services all its IP telephony calls. With the many varied tasks required of the Gatekeeper, however, the Gatekeeper tends to become overloaded, thereby slowing its operation and degrading the service it provides. When such overloading occurs, the service provider deploys additional Gatekeepers within the system to handle the additional load.
With multiple Gatekeepers, it is desirable to distribute load among the Gatekeepers. Distribution of load among Gatekeepers is generally performed during user registration, wherein a user supported by the service provider is assigned to a particular Gatekeeper. Under the H.323 Recommendation, for example, a component called Registration/Admission/Status (RAS) assigns each user of the system to a particular Gatekeeper during a registration process. However, when additional Gatekeepers are deployed, loading is not equal among the then deployed Gatekeepers, and load equalization would require de-registration of users and subsequent re-registration of the users, a burdensome process. Further, if a Gatekeeper should be down for maintenance or otherwise unavailable due to an outage, a set of users assigned to the Gatekeeper are without service. Moreover, most endpoints devices do not support RAS and are assigned to a primary Gatekeeper within the system.
Thus, there is a need in the art for an IP telephony system in which load may be distributed among multiple Gatekeepers, where load may be serviced even if an assigned Gatekeeper is unavailable and in which an overloaded Gatekeeper may lessen its loading during normal operations.
Thus, to overcome the shortcomings of the prior systems, among other shortcomings, an Internet Protocol (IP) telephony system constructed according to the present invention manages Gatekeeper load by redirecting calls from an assigned Gatekeeper to a servicing Gatekeeper during call setup. A Load Management Unit (LMU) processes all setup messages. In processing the setup messages, the LMU receives a setup message from the assigned Gatekeeper that was received from a subscriber when initiating a call. The LMU determines which Gatekeeper of a plurality of Gatekeepers should setup and service the call. Based upon its selection, the LMU either directs the assigned Gatekeeper to setup and service the call or redirects the endpoint to a servicing Gatekeeper.
Upon receipt of a redirection message, the endpoint sends a confirmation message to the assigned Gateway and then sends a setup message to the servicing Gateway. Upon receipt of the setup message, the servicing Gateway sets up and services the call. In selecting the servicing Gateway, the LMU may consider loading on each Gateway, availability of each Gateway (e.g., are any Gateways out of service), and load distribution among a plurality of Gateways, among other consideration.
A significant benefit of the LMU and operation of the present invention is that the Gateway assignment activity is performed at the time of call setup. While prior techniques assigned endpoints to Gateways at time of registration, when the endpoints placed the call, operating conditions may have changed such that the assigned Gateway was no longer a satisfactory choice in setting up and servicing the call. However, according to the present invention, Gatekeeper assignment is performed during the setup of each call. Thus, load may be dynamically balanced among the Gatekeepers, Gatekeeper outages may be accommodated without system interruption and load intended for relatively busier Gatekeepers may be redirected to relatively less busy Gatekeepers.
Moreover, other aspects of the present invention will become apparent with further reference to the drawings and specification which follow.